"Shark on!" I drop my forkful of eggs and bolt out of the lounge, pinballing off the carved wooden pillars of the Princess II as the boat rolls gently in the open swells ofthe southern Indian Ocean. I am desperate for any sighting of the creature that has obsessed me since childhood and lured me to the remote and rugged Neptune Islands, 20 miles off the coast of South Australia: the great white shark.

“Jumbo’s back!” yells Tom Pagano, an American expat living in Melbourne and one of eight passengers on a four-day journey with Rodney Fox Shark Expeditions. When I reach the upper deck, Pagano is grinning. On this ship, the shout of “Shark!” ignites thrill, not panic.

Jumbo, a female more than 17 feet in length and named for the number on her tracking tag, 747, is circling our ship. From where I stand on the upper deck she looks like a bronze airplane, her pectoral fins the wings. Pagano leans over the railing, cup of tea in hand.

“We’re gonna need a bigger boat.”

It’s the line all onboard have been waiting to say, from the 1975 movie everyone knows: Jaws. And this ship has a special connection to Jaws. The leader of our expedition, Andrew Fox, had told us how his father, Rodney, worked as a shark adviser on the film’s second unit. Andrew himself saw his first shark at age seven.

“The movie frightened a lot of people out of the water,” Fox told our group when we gathered the first night. “But it also created a large number of people who wanted to see sharks up close. They’re like the last dragons.”

These dragons have captivated me since I can remember. The great white was my favorite animal when I was growing up in landlocked Minnesota. Carcharodon carcharias, “the ragged-tooth one,” is the world’s largest predatory fish and a mystery millions of years old. At one time, great whites swam through my dreams every night. To me, sharks are everything that is wild, untamed, and unpredictable about the world.

When I was 12, my father bought me a small shark tooth sharp enough to prick a finger, and put it on a necklace. “If you wear this in the ocean,” he’d told me, “the sharks will recognize you as one of their own and won’t harm you.”

Now, as I sit on the back platform of the Princess II, my legs dangling into the open hatch of the surface cage while dive master Chris Taylor helps me with my weight belt, I think about the tooth, which I’m wearing around my neck under my wet suit. I’m impatient to get in the cage, but I also feel the edginess that keeps all of us—especially the crew—ultra-alert when the sharks are around.

A multiday expedition on the Princess II immerses guests in the world of great white sharks.

Jumbo’s large dorsal fin slices through the water a few feet from the cage as the back of the ship heaves in the swells.

“Don’t look at the cage,” Taylor advises me, tightening the belt’s straps. “Keep your eyes on the horizon; it will help you keep your balance.”

He hands me one of four regulators that connect to a central air hose, and I descend the short ladder to the bottom of the cage. My breath quickens as I feel the cold water press against my thick wet suit. I’m not a diver; it takes me a moment to acclimatize to breathing through a regulator.

Pivoting in the cage seven feet underwater, I scan the blue for any flash of white, any movement, but Jumbo is gone. The only sound is my breathing. Then the back of my neck begins to prickle. I slowly turn.

Jumbo’s pointed nose is six inches from my stomach, as close to the lower viewing window of the cage as she can get. I could touch her if I dared. She seems to consider squeezing her whalelike girth through the small window opening before dropping one of her fins and banking away. I shoot backward to the center of the cage, shaking with the shock of having a 1.5-ton shark successfully sneak up on me.

Jumbo doubles back and glides past the cage again, within arm’s length of that lower window. Her eye is not the dead matte black from the movies but brown, with a lively blue ring around the outside. She turns and passes me again, rolling onto her side to get a better look. I’m the only one in the cage, the sole focus of her attention. I drop to my knees, lean forward, and grip the metal bars. Our eyes meet, and I feel a thrill of awe and terror.

“Sharks love sneaking up on things,” Fox tells me minutes later, as he helps me out of my wet suit. “They’re ambushers. It’s safest and most efficient for them. If they know you’ve seen them, they behave differently, becoming much more wary. What’s that around your neck?”

Fox has spotted my shark tooth. Suddenly, I feel self-conscious; wearing it in front of someone whose father was famously torn open by a great white shark seems insensitive. It took 462 stitches to put Rodney Fox back together. A shark tooth is still embedded in his right wrist.

The shark bite changed the course of Rodney Fox’s life. To observe the creature that “got him,” Fox designed the world’s first shark cage so he could watch sharks in their environment in an unprovoked and, he hoped, natural state—the beginning of his evolution from shark victim to shark champion.

“This tooth of yours may be good luck,” Andrew Fox says. “You got the attention of a really special shark.”

“How many have you seen in one day?” I ask.

“Nineteen great whites in 15 minutes. Ironically, we were testing a new shark repellent device.” Fox grins.

Rodney Fox Shark Expeditions is the only outfitter in the world to offer ocean-floor cage diving, in which a shark cage is lowered to a depth of 65 feet.

“Sharks are more alert up top in case something’s up,” Fox explains. “On the bottom, they’re more relaxed and curious.”

As one of two non-dive-certified passengers on the expedition, I won’t get to try the ocean-floor cage, but I don’t miss a chance to be at ship’s edge when the cage is raised, seawater hissing out of the gaps in the bars. Invariably, the divers spit out their regulators as soon as the cage breaks the surface, talking over one another in their excitement. “Did you see that male shark just circling and circling?” Oliver Thomson, a passenger from Sydney, exclaims. “Two giant squid could have been mating behind me and I wouldn’t have noticed—or cared.”

Every one of us on the boat feels a need to talk about sharks, to put this experience into words. Evenings, when we gather after the diving is done, become my favorite time on the ship.

Author Carrie Miller meets Jumbo.

I move Fox’s camera gear off one of the benches that line the lounge to sit next to him and Ardi Tandiono, a return passenger and Singapore local. They’re examining the day’s photographs.

“Do you know this shark?” Tandiono asks Fox.

“It’s Maulder,” Fox answers. “I haven’t spotted him in a few years. I thought he may have got himself on the wrong side of the tuna industry, so I’m really happy to see him. Look,” he says, turning the laptop screen toward me. “See Maulder’s flattened dorsal fin and the hump behind? Each shark has its own markings and character. Spend enough time around them, and sharks are as easy to recognize as old friends.”

Shark research is a critical part of these multiday dive trips to the Neptune Islands. The Rodney Fox Shark team has identified and documented more than 600 great whites in the area over the past 14 years. Most expedition passengers contribute to the work, photographing sharks and gathering information during their dives.

The research isn’t without controversy. In order to draw the sharks close to the ship for tagging and identification, bait and berley (ground-up fish) are used. The berley attracts the sharks in the immediate vicinity to the boat, while the bait keeps them around the cage.

Globally, some critics say that berleying accustoms sharks to boats, teasing the sharks with bait too close to the cage and putting them at risk of damaging themselves so tourists can get those iconic wide-jawed photographs. Scientific research on this issue has been inconclusive. In Australia, shark cage diving is highly regulated: Only two operators (including Fox) are allowed to berley, and only in specific offshore areas.

Not everyone shares Fox’s affection for sharks, and many of us nurture an innate dread, carved into our DNA, of being defenseless in the ocean, vulnerable to these unseen predators. Few of us grasp sharks’ critically important role as apex predators in the marine environment. The truth is, sharks have more to fear from us than we do from them. We don’t know how many swim the oceans, but scientists are sure that even a slight shift in that delicate ecosystem will have calamitous results for marine life and the industries dependent on it.

Sharks remain a particularly touchy subject in Port Lincoln, the departure point for Rodney Fox Shark Expeditions. Port Lincoln has more millionaires per capita than any other Australian city, largely due to the $290 million that the southern bluefin tuna industry brings in annually. Many residents here know at least one person who has been killed by a shark.

“Don’t get in the cage, girl” warned the cab driver who picked me up at the airport, a rough-hewn man with matted blond hair and a Bloody Mary in a coffee cup. “Great whites are pure evil. If they’re coming for you, there’s nothing you can do about it.”

“We get a lot of shark tales here,” says Tony Ford, the head chef at Boston Bay winery, just north of Port Lincoln. He is pouring me a Sauvignon Blanc (cheekily named “Great White”) as a David Bowie song plays in the background. “People come in from the cages absolutely buzzing.”

The winery, which was established by Ford’s parents, is a place of light, with a glassed-in tasting room that overlooks rows of grape trellises marching down a hill almost to sea’s edge. It provides a stark contrast to the old pubs in town, with their darkened interiors and absence of sea views.

“Years ago we had some of the wildest bars in Australia and some of the fittest people in the world drinking in them. The men went out to sea for days, weeks. They worked hard, came home, and played even harder,” says John Plevin, a volunteer who is guiding me through the rabbit warren of rooms at the Axel Stenross Maritime Museum. Artifacts and photographs from the windjammer days of a hundred years ago fill the exhibit on my left. Plevin knows every vessel’s history—how it sailed, its catch quota, the men that worked it.

“A lot of fishermen came here. I arrived when I was 17; I’m 79 now, so I’m almost a local.” He smiles, then turns serious. “Some fishermen made good, and some went broke. But you want to know about the sharks.”

He points to a room down the stairs, past a Brobding-nagian anchor that seems to prop up the walls. “We do have a bit of a sharky history here. That’s the room you want.”

I turn the corner into a narrow space crowded with dented cages and wallpapered with newspaper clippings of attacks (including Rodney’s) and prize catches. I stand there for a long time. What I see—black-and-white photographs of great whites strung up by their tails on the docks—offers sobering evidence of our mutual fragility. The dead sharks look rubberized, fake, their power drained.

My own fragility is on my mind during an afternoon cruise in the tender boat, along the shore of South Neptune Island. A low hill of rock and scrub, the island offers the only protection from the ten-foot swells of open ocean.

Wild Eyre Peninsula is a gateway to the Neptune Islands.

The Neptunes are home to one of Australia’s largest populations of New Zealand fur seals—a favored food of great whites. So it’s no surprise that a rotating population of sharks resides in these waters. Our task this afternoon is to check on the population of sea lions and seals: On every trip Fox likes to estimate numbers and evaluate the general well-being of the colony.

Thirty minutes earlier I was in the water in the surface cage, with Maulder circling me aggressively. Rather than feeling drawn to this shark, I instinctively pulled away from it. Above me, Fox was lowering the tender boat into the ocean for our visit to the seal colony. Suddenly, Maulder disappeared, his perfectly adapted coloring allowing him to vanish in eight feet of clear water. My eyes strained to find his form in the blue. Then, abruptly, I spotted him—rising at a steep angle directly under the tender boat. He bit at the propeller, bumping the vessel’s underside.

Now I’m out of the surface cage and in the boat, cruising an area littered with shipwrecks, fully aware of what swims beneath. Rather than looking for seals, I’m scanning the water for triangular dorsal fins. It is the only time during the expedition that I feel nervous.

On our last evening, I join others for a round of Shark Dice, a baffling game with rules we passengers suspect the crew make up as they go. I can see the ship’s stern, illuminated by a halo of floodlights, and, beyond, the tarnished silver of the evening sea. Sharks are out there. Does our carousing draw them closer?

Life would be pale indeed without our dragons. Rodney Fox understands this better than anyone.

“I owe everything to the shark that bit me,” he’d said when we met in Adelaide, where he lives. “Sharks are our monsters—ours to protect and ours to love.”

That night I dream of a shark, a lone shape, suspended in the blue, swimming away from me. I wake feeling bereft, knowing the next day will be my last among the powerful creatures. Then something Rodney said returns to me.

“The mornings and nights out here, you realize you’re alone in a wilderness, on the edge of a huge ocean, and you’ve been allowed a glimpse of something otherworldly.”

I’ve had that glimpse, and will always carry it with me. My hand strays to the talisman tooth hanging around my neck and, within minutes, a peaceful sleep overtakes me.

CARRIE MILLER is a New Zealand-based writer and former Traveler staff member. Frequent National Geographic contributor MICHAEL MELFORD photographed “Jamaica, Gently” in Traveler’s October 2008 issue.